IsNumeric: Will this work?

[keeling]

Please forgive me if this is a 'dumb' question, but I am not much of a C coder.

I am working on some routines to be used in a different language. One of the routines I want is a check to see if a string is numeric (like the VB command). This is what I have come up with:

int IsNumeric(char *pString){
	char *pEnd;
	double dbl;
	dbl = strtod (pString,&pEnd);
	if (pString != pEnd && *pEnd == '\0'){
		//it is numeric
		return 0;
	}
	else{
		//it isn't
		return -1;
	}

}

I have tried a few tests with it and it seems to work, but I am great for over looking obvious.

Thanks for helping a bad c coder.

[DJMaze]

strtod() converts a string to a double or long double value and can handle numbers like
+ 1231.1981 e-1
502.85E2
+ 2010.952
strtod stops reading the string at the first character that cannot be interpreted as an appropriate part of a double value.

Your pEnd must be '\0' else it could still fail.
The (pString != pEnd) is also TRUE on values like "502.85E2 not number"

atoi()
Is another way to check numberic values but then only with integers.

[keeling]

OK, maybe I'm missing something... but isn't that what I have.

With the example you gave ...."502.85E2 not number" ... I got it to return false because it isn't a number.

Perhaps I have miss understood what you were saying. As I said, please forgive me for being a bit slow. C is not a native nor friendly tongue for me.

All I'm trying to do is make sure a string I pass to this routine is numeric. I don't care if its short or double (hence why I used strtod). I know that strtod will take leading and trailing whitespace, but I can handle that.

Thanks

[DJMaze]

pEnd points to the first character which doesn't belong to the numeric.

char *pString = "502.85E2 not number";
char *pEnd;
double dbl = strtod (pString,&pEnd);
printf("The string is '%s' the number is '%lf'\n", pEnd, dbl);

This should output: The string is ' not number' the number is '502.85E2'

[keeling]

But what I want to check is if the WHOLE string is numeric. I don't what to 'get' the numeric part.

So again, with the "502.85E2 not number" the routine SHOULD return false because it is not numeric.

Thanks again mate

[DJMaze]

It was just a small explain of your correct code.
Here's a smaller version

bool IsNumeric(char *pString){
	char *pEnd;
	double dbl = strtod (pString,&pEnd);
	return (pString != pEnd && *pEnd == '\0');
}

[keeling]

Ok, thanks.

I have to use the int type (as opposed to bool) because the language I am writing for (FreeBasic) doesn't support boolean.

Thanks again